1. Field of the Invention
The present invention relates to a method and apparatus for expanding original image data to obtain expanded-image data composed of larger number of pixels than that of the original image data.
2. Description of the Related Art
Conventionally, when expanding original image data to obtain expanded-image data composed of a larger number of pixels than that of the original image data, an interpolation processing, such as a linear interpolation, is executed. Thus, pixels are interpolated so that the expanded-image is generated. By performing the interpolation processing, a size of a digital image displayed on a display unit can be changed as required.
However, when performing the conventional interpolation processing including the linear interpolation, a variation of pixel value between pixels is not smooth, and the expanded-image data with a high-resolution can not be obtained. Namely, picture quality decreases in the process of expansion.
Therefore, an object of a present invention is to provide a method and apparatus for expanding original image data, while limiting the degradation of picture quality. An apparatus for expanding original image data according to the present invention expands the original image data. The original image data is arranged in a matrix and is composed of a determined number of pixels. The expanded-image data is partitioned into a plurality of blocks composed of a plurality of pixels. The apparatus has a magnifying power setting processor, a pixel arranger, a shifting processor, a magnifying power inspector and an expanded-image generating processor. The magnifying power setting processor sets a magnifying power regarding at least of a width direction and a length direction in the original image data. The pixel arranger arranges each pixel in said original image data at a position corresponding to a center position of each of said plurality of blocks in accordance with said magnifying power. The expanded-image generating processor generates the expanded-image data corresponding to the magnifying power by applying a fluency transform to each pixel in the original image data. Thus, the plurality of pixels in each block is generated at pixel generating positions. The magnifying power inspector inspects whether the magnifying power is odd numbered. Then, when the magnifying power is the odd numbered, the shifting processor relatively shifts the pixel generating positions with respect to each corresponding pixel of original image data by a shifting-amount, corresponding to the magnifying power, such that each arranged pixel of original image data is off-center with respect to the plurality of blocks. As the fluency transform is executed, the variation of pixel value between pixels becomes smooth, and the picture quality is maintained in the process of expansion processing. Further, the fluency transform is executed after the shifting process is performed when the magnifying power is odd numbered, so that the variation of pixel value between pixels becomes smooth.